But granting Happy and therefore other elephants a kind of legal personhood is perhaps the most roundabout way of trying to get better living conditions for her and other elephants: it comes with a low probability of success, and raises a tremendous number of questions that are difficult to answer. Many elephants deserve better living conditions, but granting them any level of personhood would potentially create an enormous legal, philosophical and financial mess that might not even succeed at getting elephants better living conditions.
For instance, rights usually come with responsibilities in the legal system — and elephants have killed people, including in the U.S. If an ill-tempered elephant is recognized as having a right to liberty and enough legal agency to protest against its living conditions, then any of its actions which infringe on the rights of others (like by injuring or killing someone while trying to escape) would seem to be punishable under the law, even though there are obviously a plethora of challenges involved in putting an elephant on trial for assault and battery or manslaughter.
Another challenges that would arise with granting even limited personhood to an animal is who would have the right to represent them, and how that would be determined. While I’m sure the Nonhuman Rights Project cares deeply about elephants, its connection to Happy is unclear; there is no evidence that they have interacted with her as much as her caregivers, or even more than the average visitor to the zoo. Another group could sue to represent Happy, claiming to have a more vested interest, creating another complication the courts would have to sort out.